SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '91c7dbd2294fa9e238db566326f33e0b293da53d35f47b0472eb53f944c105d2' 
  AND token = 'zKdnidJjPg+vsGlltZE3n7EKwShiSOpWXUtWYORA29I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}